Mechanical counter

ABSTRACT

A mechanical counter capable of showing values changing continuously and at a high rate of speed, which comprises a series of numbered drums containing e.g. six groups of 10 figures moving angularly in front of a reading window. Each drum after the first has a toothed internal gear, and each drum preceding the last has a pair of circular cams for causing periodic movement of the subsequent drum and then locking it between movement periods. This transfer movement is effected by one of a series of gear means, mounted such that each gear means consists of a first gear continuously engaged with the toothed rim of a given drum, and second and third gears each having a pitch twice that of said first gear and having their teeth alternately aligned with teeth of said first gear, so that the second and third gears are alternately moved and locked by said pair of cams. Each cam has e.g. three arcuate projections, each projection of one cam being opposite an empty space of the other cam.

I United States Patent [111 3,630,436

[72] Inventors Manuel ClaudeSanz 3,092,319 6/1963 Bright 235/117Grand-Laney, Geneva; 3,403,851 10/1968 Rechlin 235/117 Rene Weber,Geneva, both of Switzerland 3,452,927 7/1969 Bies et a1. 235/117 [21] P803.5 1970 Primary ExaminerRichard B. Wilkinson g 1971 AssistantExaminer-Stanley A. Wal

a z 1.151 d G w. E. Assign Mkmmedk y In. At orneys Gerry man an eorgeSimmons Philadelphia, Pa. Priority 1969 ABSTRACT: A mechanical countercapable of showing swltlel'hlld values changing continuously and at ahigh rate of speed, 15537/69 which comprises a series of numbered drumscontaining e.g. six groups of 10 figures moving angularly in front of areading window. Each drum after the first has a toothed internal gear,[54] MECHANIC?! 2 and each drum preceding the last has a pair ofcircular cams 13 Claims 1 8 for causing periodic movement of thesubsequent drum and [52] US. Cl 235/136, then locking it betweenmovement periods. This transfer 235/117 movement is efiected by one of aseries of gear means, [51] Int.Cl G06c 15/26 mounted such that each gearmeans consists of a first gear [50] Field of Search 235/139,continuously engaged with the toothed rim of a given drum, 136, 117 R,117 A, 1 C,91 R; 346/98 and second and third gears each having a pitchtwice that of said first gear and having their teeth alternately alignedwith Rem'ellm ciM teeth of said first gear, so that the second and thirdgears are UNITED STATES PATENTS alternately moved and locked by saidpair of cams. Each cam 2,239,460 4/1941 Levy 346/98 x has -.8- three mumProjections, each projection of one cam 2,390,444 12/1945 Mefi-erd" 235"being opposite an empty space of the other cam. 2,713,971 7/1955 Budetal 235/91 Patented Dec. 28, 197T 3,630,436

3 Sheets-S heet 1 X INVENTORS 2 f MANUEL C. SANZ RENE WEBER PatentedDec.Z8, 1971 3,630,436

3 Sheets-Sheet '2 INVENTORS FIG. 5 FIG. 6'

- MANUEL c. SANZ Rsu WEBER 6% F'FEHNl-"Y Patented Del 28, 1971 3,630,436

3 Sheets-Sheet 5 FIG. 7B A F1 B t INVENTORS & MANUELC. SANZ REN WEBERATTORNEY BY y x MECHANICAL COUNTER The present invention is a mechanicaltens-transfer counter, in the general nature of a conventional odometer.In the illustrated embodiment, four ringlike drums disposed along acommon horizontal axis bear numerical indicia for displaying afour-digit number through a window in the housing. A rotatable shaftprojecting axially from the housing is connected to the drums bysuitable gearing so that the indicia are caused to display a desiredmultiple of the number of revolutions through which the shaft hastraveled.

For the number to be displayed as a conventional decimal value, it isnecessary for the tens drum to be rotated one increment to display thenext figure each time the units drum has rotated through suchincrements. Although conventional electric or gas meters with separatedials for each figure accomplish this be simply providing a 10 to 1ratio continuous step down gearing between units and tens dials, thisproduces the possibility of confusion in an odometer-type display. Inthat event, when the units value is above about 7, the tens valuedisplayed appears to be the approaching figure rather than the precedingtens value, which should be.

Odometer displays, accordingly, conventionally provide means for holdingconstant the tens value displayed while the units display ranges from 0to 9. Then only as the units value goes from 9 to 0, the tens value iscaused to increment as well.

The present invention provides a counter which functions satisfactorilyat high rates of revolution, such that under similar use prior artdevices would generate undesirable noise and suffer excessive wear. Oneway this is accomplished in the present invention is to lower the rateof rotation of the indiciabearing drums by providing several, e.g. six,sets of indicia on each drum. I-Iere, each drum rotates at one-sixth therate at which it would have to travel if a single set of digits (0 to 9)were on its face. Of course, this makes positioning of the drum morecritical, as an increment is only 6 rather than 36.

To provide the required accurate positioning of each drum, means areprovided for transferring increments from a lower order drum to a higherorder one in a very precise manner. The higher order (e.g. tens) drumcarries an internal gear with a multiplicity of teeth out into its innercircumference. The lower order e.g. units) drum carries along its innercircumference a 'pair of internal cams which have complementaryelevations and depressions. Each elevation on each cam extends one-sixthof the circumference in the preferred embodiment and is followed by acorresponding depression extending for a similar distance, and so onaround the inside of each cam.

Associated with each drum and its pair of cams is a pair of star, orMaltese cross, gears which are fixed to each other out of phase. Thesegears are disposed so that the tooth of one gear fits into thedepression of one of the cams of the drum and the cut or shortenedportion of the other gear rides on the protrusion of the complementarycam. As the drum is rotated, the cams will pass the gears withoutchanging their position until the depressed portion of the one cam givesway to an elevated portion. At this point, the tooth of the first gearwill be kicked out of the cam depression in which it had been riding,and at the same time a tooth of the second gear will rotate into thedepression of the second cam which will have moved into position nearthe gear, replacing the protrusion of the second gear will rotate intothe depression of the second cam which will have moved into positionnear the gear, replacing the protrusion of the second cam previouslythere. This describes a single kickover" of the pair of star gears.

As the pair of star gears are fixed to a first gear which continuouslymeshes with the internal gear of the next higher order drum, the higherorder drum is thus caused to move one increment each time the star wheelassembly kicks over.

It is to be noted that the pair of star gears have not resumed thestarting position after only a single kickover, since a tooth of thesecond gear is in a depression of the second cam at the end of theoperation just described. It will be apparent that as the drum continuesto rotate, a protrusion of the second cam will force the tooth of thesecond gear out of the depression in a manner entirely analogous to thatpreviously recited and that the second kickover will result in a toothof the first star gear again being within a depressed portion of thefirst cam. The effect of the complementary sets of cam surfaces and stargears is not unlike walking; that is, the teeth of the star gears appearto walk around the inside of the drum as the drum rotates in operation.v

A further advantage may be obtained by providing additional sets ofidentical transfer wheels, disposed about the internal circumference ofthe drums. That helps to balance the application of rotational moment toeach higher order drum as it is moved by providing impetus from severalevenly spaced points. By so doing, the load on any given transfer wheelis reduced proportionally, through sharing with corresponding elements,and wear is thus further reduced.

In general, the numbering on each drum may contain n same groups of mfigures, arranged one after the other. Each cam of each pair of camswill thus have xn/2 arcuate projections, where x is a small integer. Thestar gear teeth are arranged, one in the plane of the first cam, and theother in that of the second cam, so that they each have a tooth pitchequal to 2k/x times the pitch 1r of the corresponding gear, that one ofthe series of teeth is placed at an angle in relation to the other ofk/x times the pitch 1r of the gear and finally that the externaldiameter of each star gear is such that, for a given angular position ofthe gear means to which they are associated, two adjacent teeth of onestar gear come in contact at their ends with a projection of thecorresponding cam, the tooth of the other star gear which is containedbetween the said adjacent two teeth being engaged in the hollow of theother cam facing this projection.

PREFERRED EMBODIMENT The drawings represent one example of an embodiment0 this invention, in which FIG. 1 is an axial section;

FIG. 2 is one view in section along the line Il-Il of FIG. 1;

FIG. 3 is an explanatory section of certain components of one portion ofthe counter visible in FIG. 2, along the line III- III of this Figure;

FIG. 4 is an enlarged perspective view of a driving gear of the counter;

FIG. 5 and 6 are sections along the line V-V and Vl-VI respectively ofone of the drums visible in FIG. 3;

FIGS. 7, 7A, 7B, 8, 8A, and 8B are enlarged diagrammatic views showingthe angular progression of one numbered drum of the invention.

The counter represented in the drawing has a casing 1 including acircular wall la and a cylindrical lining lb continuous with this wall,in which is cut a reading window 2, the opening of which is closed by arotating plate 3 joined to a driving axle 4 of the counter which pivotsin a mounting 5 made of synthetic antifraction material which has asupport 6 formed by circular plate with a cylindrical extension locatedin a central opening cut in the wall la.

The support 6 is fixed on the wall 10 of the casing by means of threescrews 7 arranged equidistantly from each other around the axle 4,passing through the support 6 and a ringlike crosspiece 8 and fixed byscrewing the end into a circular screw-hole plate 9.

Between the plate 3 and the wall la of the casing are four drums A, B,C, D, the external surface of each of which has six groups of 10 figuresfrom 0 to 9, arranged one after the other in each group and from groupto group as shown by the portions of the drums A and B visible in FIG. 1of the drawing.

The drum A is joined to the plate 3 by pins such as 10 and thus turnswith the latter.

The drums A, B and C have an unfixed position with regard to thepossible axis of rotation, only the drum D having a set position bydirect contact with the end of the plate of the support 6.

The lateral surface of the ringlike crosspiece 8 has three semicircularchannels 8a angularly equidistant from each other in the opening ofwhich are three axles 11, each with three gears e, f, g mounted loosely,the function of which will be shown later. The axles 11 are arrangedangularly in equidistant position and are parallel; they are fixed, atthe left end, in the appropriate openings of the support 6 and, at theright end, in corresponding seats of the screw-hole plate 9.

As can be seen in FIGS. 3, 5 and 6, the drums B and C are actuallycomposed of a ringlike piece of which one-half of the internal rim has aseries of teeth 12, 60 teeth in the example illustrated that is, anumber of teeth equal to the number of figures on the numbered drum butwhich can, in variant form, be a multiple of this number, or equal tok-m'n, if m is the number of groups of n figures and k the multiplicityfactor, k being equal to 1, 2, 3, etc.

In the second half of the internal rim each drum B and C has two cams l3and I4, ringlike in structure, the profile of which is seen in FIG. 5,for cam 13 and in FIG. 6 for cam 14.

Each cam 13 and 14 has three projections s,, s s for cam 13 and Z Z2, 2for cam 14 and three empty spaces e e e for cam 13 and f f f for cam 14of angular length slightly below that of the projections. In addition,the bottom of these spaces and the arc of the projections have a roundedprofile of which the center of curvature coincides with the center ofcurvature of the external surface of the drum.

As seen in the drawing, each projection of one of the cams is oppositeto an empty space of the other and vice versa. Thus, the projections s,,s s of the cam 13 face the respective empty spaces f,, f f of the cam14, whereas the projections 2,, 2 z of the latter are respectivelyopposite the empty spaces e 2 and e of the cam 13. It should be noted inaddition that each projection of one of the cams is linked, at each end,to the adjacent projections of the other cam by an intermediatestrengthening component r (FIG. 3).

In the application shown, the total number of projections of each drumis equal to the number n of groups of m figures appearing on theexternal surface of the drum; in this instance the number is thus six.

As a variation, the number of projections may be equal to a multiple ofn. In general, the number of projections of the two cams of each drummight be equal to xn, where x=l, 2, etc.

In the application represented in FIG. I, the four drums, A, B, C and Dare of identical structure, all having a series of teeth 12 and cams I3and 14. It should be noted that for the drum A, the teeth are notnecessary, and are not of any use, as this drum rests by means of thisseries of teeth on the external surface of the plate 9 previously noted.As a variation, the drum A could be made without the teeth 12 and haveinstead a support ring of diameter corresponding to the internaldiameter of these teeth.

Similarly, the part of the drum D composed of the earns 13 and I4 is notindispensable and is masked by the plate 16 on the surface of which thisdrum rests by means of the projections of the said cams.

As a variation, the drum D could be made without the earns 13 and 14 andhave instead a support ring of diameter corresponding to twice theradius of curvature of the profile of the arc of the difierentprojections.

As will be seen, the calculator described functions without the teeth 12for the drum A and cams l3 and 14 for drum D.

As described, the drum A is driven directly by the plate 3 to which itis joined whereas the movement of each drum B, C and D is controlled, bythe drum designed to count the next lower decimal numbers.

In the mechanical counter pictured, the drum A counts units; the drum B,tens; the drum C, hundreds; and the drum D, thousands.

The control of each drum B, C and D by the preceding drum isaccomplished by means of substantially identical gear means e, f and gpreviously noted and shown in FIG. 4.

Each gear means e, f, g has a first gear p, the teeth of which and D. Inthe application represented, the gear p of the component has eightteeth.

Each gear means e, f, g has in addition two star gears d, and d thepitch of the teeth of which is equal to twice the pitch of the teeth ofthe gear p, that is to twice the pitch of the teeth 12 of each drum.Each star gear d or d, thus has four teeth.

In general, it can be shown that for a counter each drum of which hascams with a total of xn projections and of which the series of teeth 12has a number of teeth equal to k'm-n, the pitch of the adjacent teeth d,of star gears and d must be equal to 2(k/x) times the pitch 1r of thisseries of teeth 12 or p=2 (Ir/x).

As seen in FIGS. 1 and 3, each gearing must thus cooperate at the sametime with two adjacent drums, that is by the gear p, with the toothedrim 12 of a given drum and by the teeth a and d with the two cams 13 and14 of the adjacent drum, of next lower decimal place. Towards this end,the diameters of the part of the gearing constituting the gear p andthose of the teeth of star gears d, and d as well as the position ofeach axle 11 with relation to the pivotal center of the drums are chosensuch that the gear p of each gear means is constantly engaged with thetoothed rim 12 of a drum and that the teeth of the star gears d, and doccupy with regard to the two cams l3 and 14, with which they mustcooperate, the position shown for example, in FIG. 7.

It can be seen in FIG. 7, that if one tooth d l of the star gear d isengaged in one empty space of the cam 14, the adjacent teeth d, and d,"of the star gear d situated on both sides of the tooth 11 have theirapices arranged on a circle of radius corresponding to the radius ofcurvature of the arc of the projections of the cam 13, which signifiesobviously that the teeth 11" and d," will come in contact with theprojections of this cam in the course of angular displacement of thelatter, in direction F. for example (FIG. 7).

FIG. 7 shows the position of the star gears a and d of one gear meansand the projections s. and 2 and of the empty spaces f and e; of thecams I3 and 14 at the moment when the projection Z3 of the cam 14 meetsthe tooth 1 of the star gear d It can be seen in particular that thetooth d," of the star gear d, is thus resting on the projection s of thecam 13 whereas the tooth d, is already over the adjacent empty space 83.

FIG. 8 shows the corresponding position of the gear p, associated withstar gears d and d shown on FIG. 7, and of one portion of the toothedrim 12 with which this gear p engages and belonging to the followingdrum.

When the drum with the cams l3 and 14 moves at an angle in direction F,(FIG. 7), the projection Z pushes the tooth (1 and moves the star gear din direction F which makes the tooth d, of the star gear d, penetrateinto the empty space f;, of the cam 13 and correspondingly advance thegear p and thus the toothed rim 12 of the next drum, in direction Fidentical to F This movement stops at the time that the gear means hasturned to such a degree that the tooth d occupies with regard to theprojection z, the position illustrated in FIG. 7B, a position shiftedangularly by one tooth pitch with regard to the position in FIG. 7A. Itcan be noted on FIG. 78 that the gear means is then engaged in an emptyspace e of the cam 13 by tooth d, and that it rests at the same time onthe projection 2-,, of cam 14 by the next tooth of the star gear (1;.

It follows that if the cams l3 and 14 continue to move in direction F,,the teeth d will then be in contact with the projection z; by two ofthese teeth.

What has just been stated with regard to only one gear and one portionof the cams 13 and 14 of a drum is obviously true for all the gear meansand for all the cams.

In particular, each gear means is blocked angularly be contact with theprojections of one cam while the projections of the other cam do notcontrol the angular displacement in direct F (FIGS. 7, 7A, 7B) so thatthe drum controlled by this gear is blocked angularly while it is notmoved (position have a pitch identical to that of the teeth 12 of thedrums B shown in FIG. 8 and 8B, for example).

The two cams l3 and 14 of each drum and the two star gears d and d, ofthe gear means cooperating with these cams thus act alternately tocontrol the locking of the next drum and to control the advance of thisdrum.

In addition, considering the multiplicity of projections of each cam andgear means e, f and g which the counter contains, each tooth of a stargear is used only once for one advance of the next drum equivalent totwo tooth pitches, and because there are three series of gears, withonly one-third of the expenditure which would be required if there wereonly one projection per cam and only one series of gears.

It follows that the drums of the calculator and the driving gears e, fand g can be made of synthetic resin without fear of premature breaking.

In addition, the angular displacement which each drum of the calculatordescribed must make in order to change readings by 1,000 units persecond will be one-sixth that of the traditional counter, the drums ofwhich have only one group of figures from O to 9, for example, on thesurface.

In this latter case, the first drum would have to turn, as describedabove, at a rate of 100 r.p.s., or 6,000 r.p.m. With the drum describedin this invention, this rate can be reduced to l6% r.p.s. or 1,000 rpm,the star wheel teeth d, or (1 of the gear means e each being used only500 times per minute. In the case of a counter the drums of which wouldbe numbered only from to 9 and in which the advance of each drum wouldhave to be by one figure for a complete turn of the preceding drum, theteeth d or d of a gear having the same function as the gear e of thecomputer described would be used 3,000 times per minute, or six timesmore.

It should be noted that, by the arrangement chosen, the assembly of thedrums A to D of the counter described is particularly simple as they arecentered by means of the three series of gears e, f, g which areconstantly in contact by at least one tooth of the series d, and d withone of earns 13 and 14, alternately, of the drums driving these gears.

Finally, the rotation of these drums being accomplished by mutualcontact of pieces made of synthetic material and the number andintensity of shocks intervening between the projections of the cams andthe gears being particularly small, the counter described functionsrelatively quietly, in spite of the very high speed with which it canchange readings.

In fact, and in general, the number of series of gears of a counter ofthis type depends closely on the total number xn of projections of bothcans of each drum, or on the number xn/2 of projections of each cam.

The number of gear series can be equal to xn/2 or a submultiple of xn/Zalways having a minimum value of 3, as the centering of the drumsdescribed above can be accomplished only by support of these drums on atleast three points.

Having thus described the invention, what it is desired to claim andthereby secure by Letters Patent is:

l. A mechanical counter capable of continuously counting rotationresults at a high rate of speed comprising a housing, a driven shaftreceived within said housing, a succession of different order counterdrums mounted adjacent one another for individual rotationon a commonaxis and including atleast a units and tens drum mounted for rotationwith said shaft, the remaining drums each kinematic ally independent ofthe preceding drum, said drums being supported in said housing by atleast three series of gear means, each drum having a plurality of aseries of figures on the outside periphery thereof, each drum except forsaid units drum having a gear surface with the number of teeth of saidgear corresponding to a multiple of the number of figures on theperiphery thereof, each said drum except for the last drum in successionalso having cam means, each series of gear means having one gear meansmounted so as to be in engagement with the cam means of the driving drumand the gear surface of the driven drum, the configuration of the cammeans and gear means being such that a given amount of rotation of afirst said driving drum means results in a fraction of that amount ofrotation in a second driven drum equal to one divided by the number offigures in each of said series.

2. A mechanical counter as in claim 1, further including a window meansin said housing through which said figures on said drums can be read.

3. A mechanical counter as in claim 1, wherein the gear surface of eachdrum is located on the internal annular surface of said drum and saidthree series of gear means are equally arcuately spaced within saidhousing so as to support said drums for rotation thereon, each gearmeans supporting a portion of two adjacent drums.

4. A mechanical counter as in claim 3, wherein said cam means are alsolocated on the internal annular surface of each said drum and areadjacent said internal gear surface.

5. A mechanical counter as in claim 4, wherein each said cam meansconsists of two circular cam rings, each ring having a number ofprojections equal to one-half of a multiple of the number of series offigures on the external surface of each drum, each projection having arounded profile coaxial to the pivotal axis of the drum, saidprojections being separated from each other by a distance equal to theirarcuate length, the arcuate length being equal for all said projections,each rings projections being staggered so that no project is positionedadjacent another in the other ring, and said rings being fixedly securedto each other and to the corresponding drum.

6. A mechanical counter as in claim 5, wherein each said series of gearmeans is mounted for rotation on a common axis fixed to said housing.

7. A mechanical counter as in claim 6, wherein each gear means consistsof a first gear whose teeth have a pitch equal to the pitch of the teethof the internal gear surface of said drum, said first gear being adaptedto engage said internal gear to drive said drum, and further consists ofsecond and third gears with teeth having a pitch twice the pitch of theinternal gear surface teeth of said drums, the teeth of said second gearbeing aligned with alternate teeth of said first gear and the teeth ofsaid third gear aligned with the other alternate teeth of said firstgear, said first, second and third gears being fixedly secured to eachother, the teeth of said second and their gears being adapted to engagethe projections of said internal cam rings on the driving drum.

8. A mechanical counter as in claim 7, wherein said gear teeth on saidsecond and third gears are star gears out of phase with each other, sothat when, for a given angular position of either of said two gears, twoadjacent teeth of one gear are in engagement with said rounded profileon the projections on one of said cam rings, the tooth of the other gearis in the space between two of said projections on said other cam ring.

9. A mechanical counter as in claim 8, wherein all of the components ofsaid calculator are made of a plastic material.

10. A mechanical counter capable of continuously calculating revolutionsof a shaft at a high rate of speed, said counter comprising a housing, ashaft received in said housing and adapted to be driven, a succession ofdifferent order counter drums having six series of the numbers 0 through9 on the external periphery thereof, three series of gear means mountedin said housing for rotation about a common axis and supported by saidthree series of gear means, said drums including at least a units drum,a tens drum, a hundreds drum and a thousands drum, said units drum beingcoupled to said shaft for rotation therewith, the other drums not beingoperatively coupled to said shaft, each drum beginning with said tensdrum having a surface with a gear thereon and engaged with said gearmeans, each gear having 60 teeth thereon, each said drum with theexception of said last drum having cam means, each gear means in eachseries supporting two drums by engaging the cam means of one drum andthe gear surface of an adjacent drum, each cam means and each gear meansbeing so configured that 10 revolutions of a driving drum results in lrevolution of the driven drum.

11. A mechanical counter as in claim 10, wherein the gear on each drumis on a portion of the internal annular surface of each drum, adjacentsaid gear surface, each said cam means comprising two circular ringsmounted adjacent each other inside said drum, each ring having threeprojections which have an arcuate profile coaxial with the axes of saiddrums, the arcuate length of said projections being the same and equalto the arcuate spacing between said projections, the projections of onering being adjacent the spaces on the adjacent ring.

12. A mechanical counter as in claim 11, wherein each gear meansconsists of three gears, the first gear having eight teeth whose pitchis equal to the pitch of the internal gear teeth, said first gear beingadapted to engage said internal gear to drive a drum, and furtherconsists of second and third gears each having four teeth thereon with apitch twice the pitch of the internal gear surface, the four teeth onsaid second and third gears

1. A mechanical counter capable of continuously counting rotationresults at a high rate of speed comprising a housing, a driven shaftreceived within said housing, a succession of different order counterdrums mounted adjacent one another for individual rotation on a commonaxis and including at least a units and tens drum mounted for rotationwith said shaft, the remaining drums each kinematically independent ofthe preceding drum, said drums being supported in said housing by atleast three series of gear means, each drum having a plurality of aseries of figures on the outside periphery thereof, each drum except forsaid units drum having a gear surface with the number of teeth of saidgear corresponding to a multiple of the number of figures on theperiphery thereof, each said drum except for the last drum in successionalso having cam means, each series of gear means having one gear meansmounted so as to be in engagement with the cam means of the driving drumand the gear surface of the driven drum, the configuration oF the cammeans and gear means being such that a given amount of rotation of afirst said driving drum means results in a fraction of that amount ofrotation in a second driven drum equal to one divided by the number offigures in each of said series.
 2. A mechanical counter as in claim 1,further including a window means in said housing through which saidfigures on said drums can be read.
 3. A mechanical counter as in claim1, wherein the gear surface of each drum is located on the internalannular surface of said drum and said three series of gear means areequally arcuately spaced within said housing so as to support said drumsfor rotation thereon, each gear means supporting a portion of twoadjacent drums.
 4. A mechanical counter as in claim 3, wherein said cammeans are also located on the internal annular surface of each said drumand are adjacent said internal gear surface.
 5. A mechanical counter asin claim 4, wherein each said cam means consists of two circular camrings, each ring having a number of projections equal to one-half of amultiple of the number of series of figures on the external surface ofeach drum, each projection having a rounded profile coaxial to thepivotal axis of the drum, said projections being separated from eachother by a distance equal to their arcuate length, the arcuate lengthbeing equal for all said projections, each ring''s projections beingstaggered so that no projection is positioned adjacent another in theother ring, and said rings being fixedly secured to each other and tothe corresponding drum.
 6. A mechanical counter as in claim 5, whereineach said series of gear means is mounted for rotation on a common axisfixed to said housing.
 7. A mechanical counter as in claim 6, whereineach gear means consists of a first gear whose teeth have a pitch equalto the pitch of the teeth of the internal gear surface of said drum,said first gear being adapted to engage said internal gear to drive saiddrum, and further consists of second and third gears with teeth having apitch twice the pitch of the internal gear surface teeth of said drums,the teeth of said second gear being aligned with alternate teeth of saidfirst gear and the teeth of said third gear aligned with the otheralternate teeth of said first gear, said first, second and third gearsbeing fixedly secured to each other, the teeth of said second and thirdgears being adapted to engage the projections of said internal cam ringson the driving drum.
 8. A mechanical counter as in claim 7, wherein saidgear teeth on said second and third gears are star gears out of phasewith each other, so that when, for a given angular position of either ofsaid two gears, two adjacent teeth of one gear are in engagement withsaid rounded profile on the projections on one of said cam rings, thetooth of the other gear is in the space between two of said projectionson said other cam ring.
 9. A mechanical counter as in claim 8, whereinall of the components of said calculator are made of a plastic material.10. A mechanical counter capable of continuously calculating revolutionsof a shaft at a high rate of speed, said counter comprising a housing, ashaft received in said housing and adapted to be driven, a succession ofdifferent order counter drums having six series of the numbers 0 through9 on the external periphery thereof, three series of gear means mountedin said housing on fixed axes, said drums being mounted in said housingfor rotation about a common axis and supported by said three series ofgear means, said drums including at least a units drum, a tens drum, ahundreds drum and a thousands drum, said units drum being coupled tosaid shaft for rotation therewith, the other drums not being operativelycoupled to said shaft, each drum beginning with said tens drum having asurface with a gear thereon and engaged with said gear means, each gearhaving 60 teeth thereon, each said drum with the exception of said lastdrum having cam meAns, each gear means in each series supporting twodrums by engaging the cam means of one drum and the gear surface of anadjacent drum, each cam means and each gear means being so configuredthat 10 revolutions of a driving drum results in 1 revolution of thedriven drum.
 11. A mechanical counter as in claim 10, wherein the gearon each drum is on a portion of the internal annular surface thereof andsaid cam means are also located on the internal annular surface of eachdrum, adjacent said gear surface, each said cam means comprising twocircular rings mounted adjacent each other inside said drum, each ringhaving three projections which have an arcuate profile coaxial with theaxes of said drums, the arcuate length of said projections being thesame and equal to the arcuate spacing between said projections, theprojections of one ring being adjacent the spaces on the adjacent ring.12. A mechanical counter as in claim 11, wherein each gear meansconsists of three gears, the first gear having eight teeth whose pitchis equal to the pitch of the internal gear teeth, said first gear beingadapted to engage said internal gear to drive a drum, and furtherconsists of second and third gears each having four teeth thereon with apitch twice the pitch of the internal gear surface, the four teeth onsaid second and third gears being staggered and adapted to engage theprojections on said cam rings of a driving drum, said first, second andthird gears being integral.
 13. A mechanical counter as in claim 12,wherein said second and third gears are star gears out of phase witheach other, so that when two adjacent teeth of one gear are inengagement with the arcuate profile of the projections on one of saidcam rings, the adjacent tooth of the other gear is in the space betweentwo of said projections on said other cam ring.